The present invention relates to a fan system for drawing ambient air through the radiator of an internal combustion engine cooling system.
Both engine-driven and hydraulic or electrically-driven radiator cooling fans have been used for almost a century with internal combustion engines. Such cooling fans typically include a multi-bladed element mounted upon a centrally located motor. U.S. Pat. No. 5,660,149 and U.S. Pat. No. 6,342,741, as well Published Application No. U.S. 2004/0223845 all disclose typical radiator cooling fans in which the motor is mounted at the center of the fan arrangement. This type of fan architecture suffers from one major drawback. Namely, in the event that the vehicle is being operated at a high, or even moderate, ground speed, such that ram air entering the vehicle at the front of the radiator would develop a sufficient pressure to force ambient air through the radiator, the fan blades and hub severely block the airflow. Although some fans are clutched with a thermostatic control so as to save energy, the blades and hub of such clutch fans block airflow to the central portion of the radiator, thus impairing the cooling capability of the radiator. In a nod to the possibility of using ram air cooling, U.S. Pat. No. 6,106,228 discloses louvers which open when a high pressure exists at the back of a radiator, so as to allow ram air to flow through the radiator. Unfortunately, the louvers of the '228 patent are not at the center of the radiator, where the cooling air would have the greatest beneficial effect. And, such louvers do not solve the problem of air blockage caused by the fan's hub.
A system according to the present invention utilizes a fan having an essentially hollow, fixed, annular hub which is louvered to allow controlled airflow. This allows the fan to efficiently pull air through the radiator when the hub louvers are closed, while permitting minimum restriction, and concomitantly, maximum airflow through the fan hub, when the louvers are open. This will allow optimal ram air cooling of the engine and radiator.